Chromium-rich muscovite mineralization in Zagros ophiolites in Iraqi Kurdistan: a study on fuchsite paragenetic associat
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ORIGINAL PAPER
Chromium-rich muscovite mineralization in Zagros ophiolites in Iraqi Kurdistan: a study on fuchsite paragenetic association with listvenite types Mohammad Pirouei 1,2 & Kamal Kolo 1 & Stavros P. Kalaitzidis 3 Received: 8 May 2020 / Accepted: 20 August 2020 # Saudi Society for Geosciences 2020
Abstract A recent field study in Northeastern Iraqi Kurdistan revealed the extensive occurrence of fuchsite mineral in listvenite bodies within the Zagros Ophiolites. Mineralogical and geochemical analytical techniques were applied to describe the features of the fuchsite-rich phases in relation to the various listvenite lithotypes. Fuchsite occurs in two main types: (i) as pale green flaky form infilling intensively fractured zones (type I), and (ii) as pale to intense green primary mineral crystals within the listvenite (type II). The main paragenesis associated with fuchsite includes quartz and clinochlore with variable Cr content, calcite and/or dolomite, and spinel. The results of this study suggest that fuchsite and the associated Cr-rich clinochlore have been formed as a result of metasomatic reactions of Si- and K-rich fluids with Cr-rich serpentine and Cr-spinel due to hydrothermal alteration of serpentinized peridotite within the Zagros Ophiolites. Keywords Cr-micas . Fuchsite . Hydrothermal alteration . Listvenite
Introduction Micas are abundant minerals in the earth’s crust (Milovsky and Kononov 1982), resulting from the linkage between the silicate tetrahedral sheets and the brucite or gibbsite octahedral sheets to form TOT layers. Al for Si substitutions in the tetrahedra is balanced by monovalent or bivalent cations in the interlayer site. Muscovite has the general formula of KAl2(AlSi3O10)(OH,F)2, where Ba, Ca, Cs, Na, and Rb can replace K, while Al can be replaced by Mg, Fe(II), Fe(III), Mn, Li, Cr, Ti, and V; in addition, the OH group can be substituted by F (Deer et al. 1978). The amount and speciation of transition metals are responsible for the color of mica. For Responsible Editor: Domenico M. Doronzo * Mohammad Pirouei [email protected] 1
Scientific Research Center, Soran University, PO Box 624, Soran, KRG, Iraq
2
Department of Petroleum Geosciences, Faculty of Sciences, Soran University, PO Box 624, Soran, KRG, Iraq
3
Section of Earth Materials, Department of Geology, University of Patras, 265 04 Patras, Greece
instance, 1% of MnO provides purple, while 2% gives a blue color to mica (Deer et al. 1978). Fuchsite, ideally K(Al,Cr)2AlSi3O10(OH)2, is a variety of muscovite, in which Cr replaces Al in appreciable amounts (Deer et al. 1992). Its green color is attributed to significant amounts of Cr or Fe (Randive et al. 2015). The main forming process of fuchsite is related to hydrothermal metasomatism of ultramafic rocks, and is often associated with the development of listvenites (e.g., Spiridonov 1991; Auclair and Gauthier 1993; Hall and Zhao 1995; Akbulut et al. 2006). Thus, fuchsite can be considered an indication of listvenitization. The other source of formation of
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